1. Field of the Invention
The present invention relates to a method of producing a polymeric compound that is useful as a base component for a resist composition, and also relates to a resist composition containing the polymeric compound, and a method of forming a resist pattern that uses the resist composition.
Priority is claimed on Japanese Patent Application No. 2011-130706, filed Jun. 10, 2011, the content of which is incorporated herein by reference.
2. Description of Related Art
In lithography techniques, for example, a resist film composed of a resist material is formed on a substrate, and the resist film is subjected to selective exposure, followed by development, thereby forming a resist pattern having a predetermined shape on the resist film. A resist material in which the exposed portions of the resist film become soluble in a developing solution is called a positive-type, and a resist material in which the exposed portions become insoluble in a developing solution is called a negative-type.
In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have lead to rapid progress in the field of pattern miniaturization.
Typically, these miniaturization techniques involve shortening the wavelength (increasing the energy) of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers and ArF excimer lasers are starting to be introduced in mass production. Furthermore, research is also being conducted into lithography techniques that use an exposure light source having a shorter wavelength (higher energy) than these excimer lasers, such as extreme ultraviolet radiation (EUV), electron beam (EB), and X ray.
Resist materials for use with these types of exposure light sources require lithography properties such as a high resolution capable of reproducing patterns of minute dimensions, and a high level of sensitivity to these types of exposure light sources.
As a resist material that satisfies these conditions, a chemically amplified composition is conventionally used, which includes an acid generator component that generates acid upon exposure, and a base component that exhibits changed solubility in a developing solution under the action of acid.
A resin (base resin) is generally used as the base component used in a chemically amplified resist composition.
For example, a chemically amplified resist composition for forming a positive-type resist pattern in an alkali developing process that uses an alkali developing solution as the developing solution typically contains an acid generator component and a resin component which exhibits increased solubility in the alkali developing solution under the action of acid. If the resist film formed using this resist composition is selectively exposed during formation of a resist pattern, then within the exposed portions, acid is generated from the acid generator component, and the action of this acid causes an increase in the solubility of the resin component in the alkali developing solution, making the exposed portions soluble in the alkali developing solution. Accordingly, by performing alkali developing, the unexposed portions remain as a pattern, resulting in the formation of a positive-type pattern.
As the resin component, a resin for which the polarity increases under the action of acid is generally used. As the polarity increases, the solubility of the resin in an alkali developing solution increases, whereas the solubility of the resin within organic solvents decreases. Accordingly, if a solvent developing process that uses a developing solution containing an organic solvent (an organic developing solution) is employed instead of an alkali developing process, then within the exposed portions of the resist film, the solubility in the organic developing solution decreases relatively, meaning that during the solvent developing process, the unexposed portions of the resist film are dissolved in the organic developing solution and removed, whereas the exposed portions remain as a pattern, resulting in the formation of a negative-type resist pattern. This type of solvent developing process that results in the formation of a negative-type resist pattern is also referred to as a negative tone development process (for example, see Patent Document 1).
Currently, resins that contain structural units derived from (meth)acrylate esters within the main chain (acrylic resins) are generally used as base resins for chemically amplified resist compositions that use ArF excimer laser lithography or the like, as they exhibit excellent transparency in the vicinity of 193 nm (for example, see Patent Document 2).
Here, the term “(meth)acrylate ester” is a generic term that includes either or both of the acrylate ester having a hydrogen atom bonded to the α-position and the methacrylate ester having a methyl group bonded to the α-position. The term “(meth)acrylate” is a generic term that includes either or both of the acrylate having a hydrogen atom bonded to the α-position and the methacrylate having a methyl group bonded to the α-position. The term “(meth)acrylic acid” is a generic term that includes either or both of acrylic acid having a hydrogen atom bonded to the α-position and methacrylic acid having a methyl group bonded to the α-position.
In order to improve the lithography properties and the like, the base resin includes a plurality of structural units.
For example, in the case of an aforementioned resin component that exhibits increased polarity under the action of acid, typically, a base resin is used that contains a structural unit having an acid-decomposable group that decomposes under the action of the acid generated from the acid generator component, resulting in increased polarity, and also contains a structural unit having a polar group such as a hydroxyl group, and a structural unit having a lactone structure and the like. Structural units having a polar group are particularly widely used, as they enhance the affinity with alkali developing solutions, which contributes to an improvement in the resolution.
In recent years, chemically amplified resist compositions have been proposed that include a resin component which has an acid-generating group that generates acid upon exposure and an acid-decomposable group that exhibits increased polarity under the action of acid within the structure (for example, see Patent Documents 3 to 5).
These types of resin components combine the function of an acid generator and the function of a base component, and enable a chemically amplified resist composition to be prepared using only a single component. In other words, when this type of resin component is subjected to exposure, acid is generated from the acid-generating group within the structure, and the action of that acid causes decomposition of the acid-decomposable group, thereby forming a polar group such as a carboxyl group that causes an increase in the polarity. As a result, when a resin film (resist film) formed using such a resin component is subjected to selective exposure, the polarity of the exposed portions increases, and by performing developing using an alkali developing solution, the exposed portions can be dissolved and removed, thus forming a positive-type resist pattern.